(Some sources incorrectly state that McCarran received a bachelor's degree in 1901 and a master's degree in 1915.[1] In fact, he did not receive a bachelor's degree. He received an honorary master's degree in 1915[2] and an honorary LL.D. in 1945, both from the University of Nevada.[3] In addition, he received an honorary LL.D. from Georgetown University in 1943.[4])

McCarran was also Nevada Chief Justice (1917–1918), chairman of the Nevada State Board of Parole Commissioners (1913–1918) and chairman of the Nevada State Board of Bar Examiners (1919–1932). A member of the Democratic Party, McCarran ran unsuccessfully for the U.S. Senate in 1916 and 1926. In 1932, he ran a third time, securing the Democratic nomination and defeating Republican incumbent Tasker Oddie, becoming Nevada's first native-born U.S. senator. During the 1930s, McCarran became well known as one of the few congressional Democrats who totally rejected the New Deal.

He sponsored laws concerned with the nation's security, including the Civil Aeronautics Act of 1938, the Federal Airport Act of 1945 and the Administrative Procedures Act of 1946. He was also an early advocate of a separate air force, sponsoring legislation in Congress to that effect as early as 1933.[5] He was co-sponsor of the McCarran-Ferguson Act in 1945, a law that exempted the insurance industry from most federal regulation including antitrust regulation.

McCarran made much of these records when questioning a Sinologist, Owen Lattimore, for 12 days in acrimonious testimony in February 1951. McCarran subsequently pushed very strongly for Lattimore to be indicted for alleged acts of perjury during his testimony. Lattimore's lawyer Abe Fortas accused McCarran of deliberately asking questions about arcane and obscure matters that took place in the 1930s in the hope that Lattimore would not be able to recall them properly, thereby giving grounds for a perjury indictment because of discrepancies between the records and Lattimore's testimony.

In June 1952, McCarran joined Francis Walter in instigating the passing of the McCarran–Walter Act, a bill that imposed more rigid restrictions on entry quotas to the United States. It also stiffened the existing law relating to the admission, exclusion and deportation of "dangerous" aliens as defined by the McCarran Internal Security Act. In response to the act he made a well known statement:

“

I believe that this nation is the last hope of Western civilization and if this oasis of the world shall be overrun, perverted, contaminated or destroyed, then the last flickering light of humanity will be extinguished. I take no issue with those who would praise the contributions which have been made to our society by people of many races, of varied creeds and colors. America is indeed a joining together of many streams which go to form a mighty river which we call the American way. However, we have in the United States today hard-core, indigestible blocs which have not become integrated into the American way of life, but which, on the contrary are its deadly enemies. Today, as never before, untold millions are storming our gates for admission and those gates are cracking under the strain. The solution of the problems of Europe and Asia will not come through a transplanting of those problems en masse to the United States.... I do not intend to become prophetic, but if the enemies of this legislation succeed in riddling it to pieces, or in amending it beyond recognition, they will have contributed more to promote this nation's downfall than any other group since we achieved our independence as a nation.[7]

”

The immigration provisions of the act were later superseded by the 1965 Immigration Act, but the power of the government to deny visas for ideological reasons remained on the books another 25 years after that.

McCarran Boulevard is a major roadway in Reno, Nevada, also named after the senator.

Cartoonist Walt Kelly introduced a character into his Pogo comic strip called Mole MacCaroney. Mole's near-blindness and concerns about "germs" were seen as an attack on McCarran and his immigration-restriction policies.

The senator was allegedly the inspiration for the fictional character of corrupt United States Senator Patrick Geary (also from Nevada), in the film The Godfather Part II.[9]